Communicable Diseases in Humans

This chapter covers various types of communicable diseases that we find commonly in India and often have an adverse socio-economic impact on society.

Zoonotic diseases

Zoonotic diseases are those which Spread between humans and animals.

In recent times, man-animal interaction has increased due to habitat destruction, increase in population and mobility. This has increased the chances of an infection spreading from animals to humans.

If you look at the last 25 years — in 1997, we had avian flu H5N1; in 2003, we had SARS; in 2009, we had the swine flu–H1N1 pandemic; in 2013, we had MERS in the Middle East; in 2014-15, we had Ebola and, in 2018, we had Zika. Every two or three years we have had completely new epidemics.

• Until COVID-19, we have managed to dodge the bullet.
• In the case of SARS, it was possible, with great global cooperation and aggressive diagnosis and public health measures to stop it, which was amazing. We got lucky.

But COVID-19 became the first modern Epidemic in the world.

Epidemics

Epidemic: widespread occurrence of an infectious disease in a community at a particular time.

Pandemic: An epidemic that has spread across a large region.

Epidemiology:

Epidemiology is the study of epidemics.

The basic reproduction number/ratio denoted as R₀, of an infection can be thought of as the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection.

R₀ for various Infections:

Disease	Route	R0
Measles	Airborne	12-18
Chickenpox	Airborne	10-12
Polio	Fecal-Oral route	5-7
Smallpox	Airborne droplets	3.5-6
HIV/AIDS	Body fluids	2-5
SARS	Airborne Droplets	2-5
Common Cold	Airborne droplet	2–3
Diphtheria	Saliva	1.7–4.3
COVID-19	Airborne droplet	1.4–3.9
Delta variant of COVID		6-7
1918 Influenza pandemic	Airborne droplet	1.4–2.8
2014 Ebola Outbreak	Body fluids	1.5–2.5
Tuberculosis (India)	Airborne	~1

 

• SUTRA model for charting the trajectory of COVID-19: IT is a mathematical model to predict the spread of the virus functioning under Dr. Manindra Agrawal, Professor, IIT Kanpur

Integrated Disease Surveillance Program (IDSP)

IDSP is a disease surveillance scheme under the Ministry of Health and Family Affairs, assisted by the World Bank. Aim: to strengthen disease surveillance for infectious diseases to detect and respond to outbreaks quickly. The scheme seeks to set up a Central Disease Surveillance Unit and a State Surveillance Unit in each State where data is collected and analysed. A large amount of data on disease reports is collected to be able to identify the outbreak of a disease, identify its causes and take corresponding preventive and responsive measures. An early warning system has been put into place to take timely preventive steps.

Family of Viral Diseases:

Influenza:

Influenza is a seasonal flu caused by a family of RNA viruses called the Influenza Virus.

• Vaccines are known for many viruses such as H1N1(Influenza A), H3N2 & Influenza B but institutes are not prepared for its mass- adoption. Non-availability of sufficient doses of quadrivalent vaccine and profiteering on the demand major cause of concern.
  • Quadrivalent Vaccine: 4 influenza strains. [2 A subtypes, 2 B subtypes.]
  • Trivalent Influenza Vaccine: 3 strains.
• Cases are recorded in the Integrated Disease Surveillance Programme.
  • Jan 2019 Epidemic: 31 deaths in 768 cases. Mostly in Rajasthan.
  • Other high-risk states: Maharashtra, Gujarat, Telangana & NCR
  • In the past 6 years: 42,500 cases have been registered & the death toll has touched 2,990.
• High-risk persons:
  • Health workers are at a very high risk, just as in the case of any other infectious disease.
  • Co–morbidity: people with lung, kidney, liver and heart disease, diabetics, especially in the elderly.

Avian Influenza:

Avian Influenza or Bird Flu refers to the Strains of the influenza virus that primarily infect birds, but can also infect humans. It causes a highly infectious, severe respiratory disease.

• H9N2: Indian scientists have detected the country’s first case of infection with a rare variant(a subtype of Influenza A) of the virus that causes avian influenza, or bird flu. These are found worldwide in wild birds are endemic in poultry in many areas; and can infect humans.
• H5N1 is the subtype of the Influenza A virus that was reported in ducks. Found in Alappuzha district in Dec 2021.

Its outbreak is declared by M/o Animal Husbandry, and not by M/o Health.

Transmission of bird flu: Areas bordering infected countries and in areas visited by migratory birds. For example, almost all cases of H5N1 infection in people have been associated with close contact with infected live or dead birds or H5N1-contaminated environments.

• Bird to Human: It spreads by touching contaminated surfaces. It does not infect humans easily, but once it does, the mortality rate is about 60%.
• It Can’t spread through properly prepared and thoroughly cooked food.
• Human to Human: It is difficult to transmit the infection from person to person through the respiratory route.

Swine Flu(H1N1):

Swine flu is an infection of the respiratory tract characterized by the usual symptoms of flu — cough, nasal secretions, fever, loss of appetite, fatigue, and headache.

• It was known in the past to occur in people who had been in the vicinity of pigs.
• The virus is transmitted by short-distance airborne transmission, particularly in crowded enclosed spaces. Hand contamination & direct contact are other possible sources of transmission.

Rabies:

• WHO estimates that rabies (also a zoonotic disease) costs the global economy approximately $6 billion annually. Considering that 97% of human rabies cases in India are attributed to dogs, interventions for disease management in dogs are considered crucial.
  • DAHD has partnered with the M/oHFW in the National Action Plan for Eliminating Dog-Mediated Rabies. This initiative is geared towards sustained mass dog vaccinations and public education to render the country free of rabies.

Chicken Pox:

• It is a viral infection caused by varicella–zoster virus (VZV) and is highly contagious.
• 2020: The Health Department has issued an advisory following a spurt in chickenpox cases in the Alappuzha District of Kerala.

Nipah Virus:

Transmission is possible only through Direct contact with other humans with:

1. Through Bats: It can be transmitted through urine, faeces, saliva and birth fluids of bats to humans who climb trees coconut or pine trees for harvesting or drinking raw pine. For example, Kerala Cases in 2018.
2. Infected pigs or any domesticated animals can also spread the Nipah virus.

Rift Valley Fever (RVF):

In 2016, WHO received reports about unexplained deaths among humans, along with death and abortion in livestock in the North Western parts of Niger, and the areas bordering Mali.

• Host: sheep and cow.
• Transmission through blood;
• It is a viral disease. Those who have bleeding have a high chance of death. At present, it does not appear that one person can infect another person.
• It is most commonly seen in domesticated animals in sub-Saharan Africa, such as cattle, buffalo, sheep, goats, and camels. People can get RVF through contact with blood, body fluids, or tissues of infected animals, or through bites from infected mosquitoes.
• Its outbreak was reported in 2006/07 in Kenya and Somalia and 2010 in South Africa outbreak.

Monkeypox

Monkeypox is a rare viral infection that is usually linked to travel to Central or West Africa.  Since it was first identified in a colony of monkeys in Copenhagen in 1958, monkeypox has been largely overlooked by the Western world. An infectious poxvirus that causes fever, chills and rashes, the disease is endemic, or consistently regionally present, in ten African countries.

• It can spread through animals via:
  • Direct contact with lesions, body fluids
  • Animal bites or scratches
  • Eating products made of infected animals
• Person-to-person spread:
  • Respiratory droplets and contaminated materials such as bedding. Thus extended close contact can lead to its spread.
  • Direct contact with rashes, scabs or body fluids.
• The spread:
  • Invasion period: It can last up to 5 days. It is characterized by fever, intense headache, lymphadenopathy, Back pain, Myalgia, and Intense asthenia.
  • Skin eruption: usually begins within 1-3 days of fever.
  • The rashes tend to be concentrated more on the face and the extremities rather than on the trunk.

Bacterial origin diseases

Those diseases which are caused by Bacteria are a bit different from the viral infections in terms of their treatment. On these diseases, antibiotics can work and therefore are more controllable even without vaccine. However, in recent times, Antibiotic resistance has become a great threat.

Tuberculosis

Tuberculosis (TB) is caused by Mycobacterium Tuberculosis. It is a respiratory illness and spreads through the air. It mimics other diseases, confusing doctors and delaying diagnosis, but has a very high mortality of 11.5%.

• But cough and blood in sputum occur only in TB. Doctors don’t think of TB until other treatments fail.
• About 1/3rd of the world’s population is diagnosed with latent TB (without evidence of clinically manifested active TB), which means they have been infected by the TB bacteria from actively sick people without their knowledge.
• It is both treatable and preventable.
• Vaccine: Bacille Calmette-Guérin (BCG).

TB in India

India has the highest number of TB patients in the world, i.e. about 2.8 million compared to 10mn globally; What is more worrisome is that according to a Union Health Ministry report, most of the TB varieties in India are Drug-resistant (Anti-biotic Resistance):

• DR-TB: 28% of cases had resistance to one or the other anti-TB drug.
• MDR-TB: 6.19% had Multi-drug resistance TD: about 1.5L cases.
• XDR TB: 2,666 cases are extensively drug-resistant; Resistant to all known medicines.
• Totally drug-resistant TB (TDR-TB): Resistant to all the 1st- and 2nd-line TB drugs.

India’s TB Elimination Target

India aims to eliminate TB by 2025, far quicker than SDG’s global elimination target is 2030, and WHO’s target of elimination by 2035.

WHO’s End TB Strategy – 2035 Goals: 95% reduction in death, 90% reduction in TB incidence rate, 0 Catastrophic costs.

However,  currently, its incidence is declining by 1.2%/year; it needs to be 15-20% to hit the target.

India’s Strategy now is:

• Identification: Early diagnosis of TB is the key to controlling it. We need to diagnose TB before it shows its characteristic symptoms of cough and blood in sputum.
• Universal treatment: It seeks to make the daily treatment regimen universal. Every country that has reduced TB incidence practices Universal health care.
• Private sector: Patients approaching the private sector will be provided with free treatment. Also for better cooperation, the government has announced that doctors & pharmacists could be jailed for up to 2 years for failing to report new cases.
• Drug-resistant TB (DR-TB) patients: The emphasis will be on undertaking universal testing for DR-TB instead of waiting for patients to walk in to get tested. New Generation drugs (Bedaquiline and Delaminid) are recommended by WHO. India has been able to achieve enough availability of both drugs in the required numbers in recent times.

National Initiatives:

• 24th March: National TB Day
• Annual India Tuberculosis Report: is published every year.
• National Strategic Plan 2017–25 envisions achieving a “TB-free India” or “TB Mukt Bharat” by the year 2025. It provides year-wise targets for treatment, financial support and prevalence of the disease. It aims to achieve Universal Access to TB control services.
• National Strategic Plan for Elimination of TB or National Tuberculosis Elimination Program (NTEP) with the goal of elimination of TB by 2025.
  • It provides various free-of-cost, quality tuberculosis diagnosis and treatment services across the country through the government health system.
  • It seeks to employ the WHO-recommended TB control strategy, DOTS(Directly Observed Treatment, Short Course), in the Indian scenario.
• NIKSHAY Abhiyan: Provision of four DBT schemes of the programme –
  • NIKSHAY Poshan Yojana(April’18): incentives for nutritional support to TB patients.
  • The Incentive to Treatment Supporters
  • Incentives to Private Providers and
  • Transport incentive to TB patients in the notified tribal areas.
  • NIKSHAY Patrika: Quarterly newsletter on TB.
  • Problem: There are 18L registered TB patients in the country. Only 4.69L or barely 26% of the beneficiary pool, have received cash transfers so far. This is partially due to the non-updation of bank account details.
• Dare2eraD TB: Department of Biotechnology launched Data-Driven Research to Eradicate TB- “Dare2eraD TB”. It will be the umbrella TB program of DBT comprising of following key initiatives-

1. InTGS – Indian Tuberculosis Genomic Surveillance Consortium – It is proposed on lines of the Indian SARS-CoV-2 Genomic Consortia (INSACOG), to fully understand the biological characteristics of Mycobacterium tuberculosis (Mtb) and the effect of the mutations on transmission, treatment and disease severity.
2. InTBK Hub- Indian TB Knowledge Hub- Webinar Series;
3. Host-directed therapies against TB and developing an evidence-based regimen for treating extra-pulmonary Tuberculosis.
   • Analysing the genomic data of the organism is essential as the Whole Genome Sequencing (WGS) is increasingly gaining traction as an important molecular tool for Tuberculosis surveillance.
   • Effective use of the WGS technology would allow rapid identification of the origin and drug resistance (DR) profile of the TB strains in the patients. This would in turn facilitate treatment strategies for better control of TB transmission to reduce disease burden.

Other initiatives:

• The Department of Biotechnology, M/o Science & Technology has also cultivated international partnerships for Tuberculosis research.
• The Regional Prospective Observational Research in Tuberculosis (RePORT) India initiative, a bilateral collaborative effort is being supported under the aegis of the Indo-US Vaccine Action Programme (VAP), to advance tuberculosis (TB) research in India.
• The Department has initiated a major network programme on“MDR-TB in North East India: a genomic driven approach” involving 22 NER institutes from 8 states and 14 other Institutes.

Recently, the World Bank and the Government of India signed a loan agreement of $400 million for the Program Towards Elimination of Tuberculosis.

Typhoid:

Typhoid is a life-threatening bacterial infection caused by the Salmonella Typhi bacteria.

• Transmission: It can be spread through contaminated food or water.
• It affects the intestines and sometimes the bloodstream.

WHO recommends three vaccines to help control typhoid:

1. Injectable typhoid conjugate vaccine (TCV) for children and adults.
   • The “Typbar TCV”, manufactured by Bharat Biotech in India, is the world’s 1^st conjugate vaccine prequalified by the WHO.
   • Interstingly, Pakistan became the 1^st country to introduce the Indian TCV in its national immunisation program against extensively drug-resistant (XDR) typhoid outbreaks, with the help of international funding.
2. An injectable unconjugated polysaccharide vaccine (Vi-PS vaccine) for people aged two and above
3. An oral live attenuated Ty21a vaccine in capsule formulation for people over six years of age.

Salmonella

Salmonella is a group of bacteria that can cause food-borne illnesses known as salmonellosis that affects the intestinal tract (spread by the faecal-oral route). WHO identifies Salmonella as one of four key global causes of diarrhoeal diseases. Person-to-person transmission can also occur through the faecal-oral route. In humans, it is generally contracted through the consumption of contaminated food of animal origin (mainly eggs, meat, poultry, and milk). Other foods, including green vegetables contaminated by manure, have been implicated in its transmission.

Trachoma

A chronic infective eye disease. It is one of the causes of avoidable blindness and one of the 18 Neglected Tropical Diseases (NTD).

• Caused by: bacterium Chlamydia trachomatis.
• Transmission:
  • Through contact with eye/nose discharge of infected people, particularly of young.
  • It is also spread by flies that come in contact with the infected person and is most common in poor environments, low personal hygiene and inadequate access to water.
• Criteria used by WHO for assessing a country’s claim for having eliminated trachoma as a public health problem.
  • Less than 5% of children aged 1–9 years have signs of active trachoma which can be treated with antibiotics, in each previously-endemic district;
  • Less than 0.2% of people aged 15 years and older have trachomatous trichiasis, which requires eyelid surgery, in each previously-endemic district; and
• A health system that can identify and manage new cases of trachomatous trichiasis.
• Global Initiatives for Trachoma :
  • WHO’s SAFE (Surgery, Antibodies, Facial cleanliness, Environmental improvement) strategy (1997) and Global Elimination of Blinding Trachoma by 2020 to eliminate Trachoma.
  • GET2020– a WHO International Alliance of interested parties who work for the elimination of Trachoma also known as the Alliance for Global Elimination of Trachoma by 2020. M/o H&FW in 2017 declared India infective trachoma-free under the WHO GET2020 program.
• During the 1950s, India was a hyper-endemic to Trachoma. About 50%-80% of children from North-west India were affected by it. India eliminated it in 2017.

Vector Borne diseases

Those diseases which require Vectors such as mosquitoes for their transmission are known as vector-borne diseases.

Malaria:

Malaria is a vector-borne disease caused by parasitic protozoans belonging to the Plasmodium type. It is most commonly transmitted by an infected Female Anopheles Mosquito.

World’s first Malaria Vaccine: RTS, S

India accounts for 1.7% of Malaria cases and 1% of the deaths according to WHO.

• In India, malaria parasites are found more in forest areas and plains.
• Most malaria cases are mainly concentrated in tribal and remote areas of the country.
• Six states: Odisha(40%), Jharkhand(20), Chhattisgarh(20), Meghalaya, AP  & Mizoram(5-7%).  These states, along with tribal areas of MP and Maharashtra account for 90%.

Global technical strategy for malaria 2016-2030:

working in 21 countries, spanning five regions, to scale up efforts to achieve a lower malaria burden by 2030.

• E-2020 Initiative: supported by WHO where 10 countries were identified by WHO in 2016 as having the potential to become malaria-free by 2020. Of these five countries China, Iran, Malaysia, Timor-Leste  & El Salvador reported no indigenous cases of malaria in 2018.

Steps taken by India:

• National Strategic Plan (NSP) for Malaria Elimination (2017-22): Mo Health & Family Welfare. It has set the malaria elimination deadline as 2027, SDG: 2030.
• Five-year National Strategic Plan for Malaria Elimination: This marked a shift from the strategy of “control” to “elimination”. It provides a roadmap to achieve the target of ending malaria in 571 districts out of India’s 678 districts by 2022.
• Odisha’s Durgama Anchalare Malaria Nirankaran(DAMaN) initiative has shown impressive results in a short period. In 2017, ASHA workers helped distribute approximately 11Mn bed nets under this initiative. This recorded an 80% decline in malaria cases and deaths in 2017.
  • It also aims to deliver services to the most inaccessible and hardest people of the state hit.
  • It has in-built innovative strategies to combat asymptomatic Malaria.

Wolbachia Bacteria

Its prevalence in Mosquitoes is correlated with a decrease in Malaria and Dengue. World Mosquito Program introduced Wolbachia in Aedes Mosquito; for their spread through natural breeding. Recently successful experiments were conducted in Australia, which demonstrated the positive correlation between the presence of Wolbachia bacteria in mosquitoes and the reduced spread of diseases such as Malaria and Dengue. Wolbachia is a tiny bacterium that is present in up to 60% of all species of insects, including several mosquito species (except the Aedes aegypti mosquito: responsible for transmitting dengue, chikungunya and Zika).

Aedes Aegypti Mosquito-borne diseases

The Aedes Aegypti mosquito is a very common species of mosquito identified by the white and black stripes on its legs. It can breed in stagnant water and is often found in the rice fields.

It acts as a host to the flavivirus, which causes types of fevers such as Dengue, Yellow fever, Japanese Encephalitis (JE) and West Nile fever. It also acts as the reservoir for the Chikungunia virus (CHIKV). All of these diseases have one characteristic in common, they are associated with a significant decrease in the platelet count.

The transmission of these diseases mainly intensifies during the rainy season, during which vector populations increase.

• Japanese Encephalitis (JE): JE primarily affects children. Most adults in endemic countries have natural immunity after childhood infection, but individuals of any age may be affected.

• • Major JE outbreaks occur every 2-15 years. Recently it has claimed 54 lives in Odisha’s backward Malkangiri district in just more than a month.
  • There is no specific therapy for JE. Intensive supportive therapy is indicated.
  • It can be detected by the ELISA Test.

• Dengue is a viral disease that spreads through female mosquitoes of the Aedes variety, usually biting during the early morning and evening. Recently, the world’s 1st case of dengue being transmitted through sex was detected too.

• • It is detected by the ELISA test.

• Chikungunya Virus: It has no cure; treatment only to relieve symptoms.

• • It is detected by the ELISA test. However, In 2018, scientists have developed a biosensor technique to detect chikungunya Virus DNA.

• West Nile fever: It is endemic to many districts in Kerala in the area around Mallapuram district. It is serologically similar to the JE virus, which means a go-to test, ELISA, often fails to differentiate JE antibodies from WNV antibodies. Thus it is difficult to alert the authorities.

• • It is detected by the PCR test.

• Zika Virus causes the Gillian Barre Syndrome which causes birth-related defects. It Spreads through Mosquito to Human and Human to Mosquito transmission, Sexual transmission and pregnant woman to Foetus (Microcephaly).

• • It is detected by the PCR test.

• Yellow Fever: an acute viral haemorrhagic disease transmitted by mosquitoes, belonging to the Aedes and Haemogogus species.
  • Symptoms: fever, headache, jaundice, muscle pain, nausea, vomiting and fatigue.
  • The virus is endemic in tropical areas of Africa and Central and South America.
  • Its vaccine is available and a single dose of yellow fever vaccine is sufficient to grant sustained immunity and life-long protection.
  • WHO launched the Eliminate Yellow Fever Epidemics strategy in 2017.
  • According to a recent study, the burden and geography of yellow fever are projected to shift to Central and East Africa from West Africa by 2050. Climate change-related factors, including temperature and rainfall, would lead to this.
  • It can be detected by both ELISA and PCR tests.

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